Drug delivery methods, structures, and compositions for nasolacrimal system

ABSTRACT

A drug insert is configured for use with an implant. The implant is configured for insertion into a lacrimal canaliculus. The drug insert includes a drug core comprising a therapeutic agent and a polymer; and a sheath body comprising material substantially impermeable to the therapeutic agent, wherein the drug core is positioned within the sheath body. The sheath body is configured to provide an exposed end of the drug core that releases therapeutic agent to an eye when the drug insert is disposed within the implant and the implant is positioned in the lacrimal canaliculus. A distal end of the drug core is sealed with a medical-grade adhesive.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/332,219, filed Dec. 10, 2008 and currentlypending, which is a continuation of U.S. patent application Ser. No.11/695,537, filed Apr. 2, 2007 and currently pending, which claims thebenefit of priority under 35 U.S.C. §119(e) from U.S. ProvisionalApplication No. 60/787,775 filed Mar. 31, 2006, and U.S. ProvisionalApplication No. 60/871,864, filed Dec. 26, 2006, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present application is related to implants for use in or near thenasolacrimal drainage system, with embodiments providing canalicularimplants, lacrimal sac implants, punctal plugs and punctal plugs withdrug delivery capabilities.

A variety of challenges face patients and physicians in the area ofocular drug delivery. In particular, the repetitive nature of thetherapies (multiple injections, instilling multiple eye drop regimensper day), the associated costs, and the lack of patient compliance maysignificantly impact the efficacy of the therapies available, leading toreduction in vision and many times blindness.

Patient compliance in taking the medications, for example instilling theeye drops, can be erratic, and in some cases, patients may not followthe directed treatment regime. Lack of compliance can include, failureto instill the drops, ineffective technique (instilling less thanrequired), excessive use of the drops (leading to systemic sideeffects), and use of non-prescribed drops or failure to follow thetreatment regime requiring multiple types of drops. Many of themedications may require the patient to instill them up to 4 times a day.

In addition to compliance, the cost of at least some eye dropmedications is increasing, leading some patients on limited incomes tobe faced with the choice of buying basic necessities or instead gettingtheir prescriptions filled. Many times insurance does not cover thetotal cost of the prescribed eye drop medication, or in some cases eyedrops containing multiple different medications.

Further, in many cases, topically applied medications have a peak oculareffect within about two hours, after which additional applications ofthe medications should be performed to maintain the therapeutic benefit.In addition, inconsistency in self-administered or ingested medicationregimes can result in a suboptimal therapy. PCT Publication WO 06/014434(Lazar), which is incorporated herein by reference in its entirety, maybe relevant to these and/or other issues associated with eye drops.

One promising approach to ocular drug delivery is to place an implantthat releases a drug in tissue near the eye. Although this approach canoffer some improvement over eye drops, some potential problems of thisapproach may include implantation of the implant at the desire tissuelocation, retention of the implant at the desired tissue location, andsustaining release of the drug at the desired therapeutic level for anextended period of time. For example in the case of glaucoma treatment,undetected and premature loss of an implant can result in no drug beingdelivered, and the patient can potentially suffer a reduction in vision,possibly even blindness.

In light of the above, it would be desirable to provide improved drugdelivery implants that overcome at least some of the above mentionedshortcomings.

BRIEF SUMMARY OF THE INVENTION

The present invention provides implant devices, systems and methods fordelivery of a therapeutic agent from a punctum of a patient oculartissues.

In a first aspect, embodiments of the present invention provide animplant for insertion into a punctum of a patient. The punctum providesa flow path for a tear fluid from an eye to a canalicular lumen. Theimplant comprises a body. The body has a distal end, a proximal end, andan axis therebetween. The distal end of the body is insertable distallythrough the punctum into the canalicular lumen. The body comprises atherapeutic agent included within an agent matrix drug core. Exposure ofthe agent matrix to the tear fluid effects an effective therapeuticagent release into the tear fluid over a sustained period. The body hasa sheath disposed over the agent matrix to inhibit release of the agentaway from the proximal end. The body also has an outer surfaceconfigured to engage luminal wall tissues so as to inhibit expulsionwhen disposed therein.

In some embodiments, the agent matrix comprises a non-bioabsorbablepolymer, for example silicone in a non-homogenous mixture with theagent. The non-homogeneous mixture may comprise a silicone matrixsaturated with the therapeutic agent and inclusions of the therapeuticagent.

In many embodiments, the outer surface of the body can be disposed onthe sheath, and the outer surface may define a body shape that inhibitsexpulsion of the body from the punctum. The body may further comprise asupport structure over the agent matrix. The support structure maydefine the outer surface and be configured to inhibit expulsion of thebody from the punctum. In specific embodiments, the support structurereceives the sheath and agent matrix drug core therein, and inhibitsinadvertent expulsion of the agent matrix in use. The support structurecan comprise a helical coil. The support structure may have a receptacletherein, and the receptacle may fittingly receive the sheath and agentmatrix therein so as to allow unrestricted fluid communication betweenthe proximal end and the tear film in use. The outer surface may expandradially when released within the punctum, and the radial expansion mayinhibits the expulsion from the punctum.

In specific embodiments, the agent comprises a prostaglandin analogue,and the extended period comprises at least 3 months.

In many embodiments, an implant for insertion into a patient isprovided. The patient having path for tear fluid associated with an eye,and the implant comprises a body. The body can comprise a therapeuticagent and a support structure. The body can be configured to, whenimplanted at a target location along the tear fluid path, release aquantity of the therapeutic agent into the tear fluid each day for asustained release period of days. The quantity can be significantly lessthan a recommended daily drop-administered quantity of the therapeuticagent. For example, the quantity can be less than 10% of the recommendeddrop-administered quantity. In specific embodiments, the quantity can beless than 5% of the recommended drop-administered quantity.

In many embodiments, the period comprises at least three weeks and maycomprise at least three months. The therapeutic agent may compriseTimolol maleate. The body may comprise in a range from about 270 μg toabout 1350 μg of the therapeutic agent. The quantity released each daycan be in a range from about 20 μg to about 135 μg.

In many embodiments, the therapeutic agent may comprise a prostaglandinanalogue, for example Latanoprost and/or Bimatoprost, and the body cancomprise therapeutic agent in a range from about 3 μg to about 135 μg.The quantity can be in a range from about 5 ng to about 500 ng. Inspecific embodiments, the body may comprise therapeutic agent in a rangefrom about 5 μg to about 30 μg, and the quantity can be in a range fromabout 10 ng to 150 ng.

In another aspect, embodiments of the present invention provide a methodof delivering a therapeutic agent to an eye having associated tearfluid. The method comprises placing a drug core in a canaliculus of theeye. The drug core comprises a matrix and inclusions of the therapeuticagent within the matrix. A portion of the drug core is exposed to thetear. The therapeutic agent is released to the tear of the eye. Thetherapeutic agent dissolves into the matrix such that the matrix remainssubstantially saturated with the therapeutic agent while the therapeuticagent is released through the exposed portion at therapeutic levels overa sustained period.

In many embodiments, a rate of release is substantially determined bysolubility of the agent in the core, the solubility of the agent in thetear and an area of the exposed portion. The drug can be releasedthrough the exposed portion at therapeutic levels for about 90 days. Thetherapeutic agent may comprise a prostaglandin analogue, and theinclusions of the therapeutic agent comprise an oil. The therapeuticagent can be encapsulated within the matrix, and the matrix may comprisea non-bioabsorbable polymer.

In many embodiments, the therapeutic agent has a solubility in water ofless than about 0.03% percent by weight. The therapeutic agent can bereleased at therapeutic levels in response to a surfactant of the tear.A sheath may be disposed over the core to define the exposed portion,and the exposed portion oriented toward the eye on a proximal end of thecore.

In many embodiments, a punctal plug to treat glaucoma is provided. Theplug comprises a body no more than about 2.0 mm across. When inserted inthe punctum for 35 days the body delivers at least a therapeuticquantity of therapeutic agent each day of the 35 days. In someembodiments, the body no more than about 2.0 mm across comprises a crosssectional size no more than about 1.0 mm across while inserted into thepatient. In specific embodiments, the body comprises a drug core and thetherapeutic agent is delivered from the drug core. The drug core may beno more than about 1 mm across, and the body may be no more than about 2mm in length.

In many embodiments, a method of treating glaucoma is provided with apunctal plug, The method comprises eluting at least 10 ng per day of atherapeutic agent from the punctal plug for at least 90 days. Inspecific embodiments, the therapeutic agent comprises at least one ofBimatoprost or Latanoprost. The therapeutic agent may have a solubilityin water no more than about 0.03% by weight.

In many embodiments, a punctal plug to treat glaucoma is provided, theplug comprises a body. The body comprises a therapeutic agent, and thebody is adapted to release the therapeutic agent at therapeutic levelsin response to a surfactant of the eye. In specific embodiments, thetherapeutic agent has a solubility in water no more than about 0.03% byweight. The therapeutic agent may comprise cyclosporin.

In many embodiments, a punctal plug to treat glaucoma is provided. Theplug comprises a plug body. The body comprises a therapeutic agent. Thebody is adapted to release from about 80 to 120 ng of the therapeuticagent into a tear of the eye for at least about 20 days. In specificembodiments, the therapeutic agent may comprise at least one ofBimatoprost or Latanoprost.

In some embodiments, a punctal plug to treat glaucoma is provided. Thepunctal plug comprises a body. The body comprises therapeutic agentstored within a volume no more than about 0.02 cm³. The body is adaptedto deliver therapeutic levels of the therapeutic agent for at leastabout 1 month. In specific embodiments, the body is adapted to deliverthe therapeutic agent at therapeutic levels for at least about 3 months.The body can be adapted to deliver the therapeutic agent with asubstantially zero order release rate for the at least one month.

In some embodiments, composition of matter to treat glaucoma of an eyehaving an associated tear is provided. The composition comprisesinclusions. The inclusions comprise a concentrated form of a therapeuticagent. The therapeutic agent comprises a solubility in water no morethan about 0.03% by weight. A silicone matrix encapsulates theinclusions. The therapeutic agent is soluble in the silicone matrix torelease the therapeutic agent from the silicon matrix into the tear attherapeutic levels. In specific embodiments, the therapeutic agentinclusions are encapsulated within the silicon matrix comprise aninhomogeneous mixture of the inclusions encapsulated within the siliconmatrix. The inclusions can comprise Latanoprost oil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-1 and 1-2 show anatomical tissue structures of the eye suitablefor use with implants, according to embodiments of the presentinvention;

FIG. 1A shows a top cross sectional view of a sustained release implantto treat an optical defect of an eye, according to an embodiment of thepresent invention;

FIG. 1B shows a side cross sectional view of the sustained releaseimplant of FIG. 1A;

FIG. 1C shows a perspective view of a sustained release implant with acoil retention structure, according to an embodiment of the presentinvention;

FIG. 1D shows a perspective view of a sustained release implant with aretention structure comprising struts, according to an embodiment of thepresent invention;

FIG. 1E shows a perspective view of a sustained release implant with acage retention structure, according to an embodiment of the presentinvention;

FIG. 1F shows a perspective view of a sustained release implantcomprising a core and sheath, according to an embodiment of the presentinvention;

FIG. 1G schematically illustrates a sustained release implant comprisinga flow restricting retention element, a core and a sheath, according toan embodiment of the present invention;

FIG. 2A shows a cross sectional view of a sustained release implant withcore comprising an enlarged exposed surface area, according to anembodiment of the present invention;

FIG. 2B shows a cross sectional view of a sustained release implant witha core comprising an enlarged exposed surface area, according to anembodiment of the present invention;

FIGS. 2C and 2D show perspective view and cross sectional views,respectively, of a sustained release implant with a core comprising areduced exposed surface area, according to an embodiment of the presentinvention;

FIG. 2E shows a cross sectional view of a sustained release implant witha core comprising an enlarged exposed surface area with an indentationand castellation, according to an embodiment of the present invention;

FIG. 2F shows a perspective view of a sustained release implantcomprising a core with folds, according to an embodiment of the presentinvention;

FIG. 2G shows a perspective view of a sustained release implant with acore comprising a channel with an internal porous surface, according toan embodiment of the present invention;

FIG. 2H shows a perspective view of a sustained release implant with acore comprising porous channels to increase drug migration, according toan embodiment of the invention;

FIG. 2I shows a perspective view of a sustained release implant with aconvex exposed drug core surface, according to an embodiment of thepresent invention;

FIG. 2J shows a side view of a sustained release implant with a corecomprising an exposed surface area with several soft brush-like membersextending therefrom, according to an embodiment of the presentinvention;

FIG. 2K shows a side view of a sustained release implant with a drugcore comprising a convex exposed surface and a retention structure,according to an embodiment of the present invention;

FIG. 2L shows a side view of a sustained release implant with a drugcore comprising a concave indented surface to increase exposed surfacearea of the core, according to an embodiment of the present invention;

FIG. 2M shows a side view of a sustained release implant with a drugcore comprising a concave surface with a channel formed therein toincrease an exposed surface area of the core, according to an embodimentof the present invention;

FIG. 3A shows an implant with a sheath body with extensions that attachthe sheath body and core to the retention element, according to anembodiment of the present invention;

FIG. 3B shows an implant with a retention element with an extension thatretains a sheath body and a core, according to an embodiment of thepresent invention;

FIGS. 4A and 4B show a cross-sectional view of an implant with aretention structure that is shorter in length while in a largecross-sectional profile configuration than a small cross-sectionalprofile configuration, according to an embodiment of the presentinvention;

FIGS. 5A to 5C schematically illustrate replacement of a drug core and asheath body, according to an embodiment of the present invention;

FIGS. 6A to 6C show deployment of a sustained release implant, accordingto an embodiment of the present invention; and

FIGS. 7A and 7B show elution data of Latanoprost at day 1 and day 14,respectively, for the three core diameters of 0.006, 0.012 and 0.025inches and three Latanoprost concentrations of approximately 5%, 11% and18%, according to embodiments of the present invention;

FIG. 7C shows elution data for Latanoprost from 0.32 mm diameter, 0.95mm long drug cores with concentrations of 5, 10 and 20% and drug weightsof 3.5, 7 and 14 ng, respectively, according to embodiments of thepresent invention;

FIGS. 7D and 7E show dependence of the rate of elution on exposedsurface area of the drug core for the three core diameters and the threeconcentrations as in FIGS. 7A and 7B Latanoprost at day 1 and day 14,respectively, according to embodiments of the present invention;

FIG. 8A shows elution profiles of cyclosporine from drug cores into abuffer solution with surfactant and a buffer solution with surfactant,according to embodiments of the present invention;

FIG. 9A shows normalized elution profiles in nano-grams per device perday over 100 days for bulk sample of silicone with 1% Bimatoprost,according to embodiments of the present invention.

FIG. 10A shows profiles of elution of Latanoprost from the cores forfour formulations of Latanoprost according to embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-1 and 1-2 show anatomical tissue structures of an eye 2 suitablefor treatment with implants, according to an embodiment of the presentinvention. Eye 2 includes a cornea 4 and an iris 6. A sclera 8 surroundscornea 4 and iris 6 and appears white. A conjunctival layer 9 issubstantially transparent and disposed over sclera 8. A crystalline lens5 is located within the eye. A retina 7 is located near the back of eye2 and is generally sensitive to light. Retina 7 includes a fovea 7F thatprovides high visual acuity and color vision. Cornea 4 and lens 5refract light to form an image on fovea 7F and retina 7. The opticalpower of cornea 4 and lens 5 contribute to the formation of images onfovea 7F and retina 7. The relative locations of cornea 4, lens 5 andfovea 7F are also important to image quality. For example, if the axiallength of eye 2 from cornea 4 to retina 7F is large, eye 2 can bemyopic. Also, during accommodation, lens 5 moves toward cornea 4 toprovide good near vision of objects proximal to the eye.

The anatomical tissue structures shown in FIG. 1-1 also include thelacrimal system, which includes an upper canaliculus 10 and a lowercanaliculus 12, collectively the canaliculae, and the naso-lacrimal ductor sac 14. The upper and lower canaliculae terminate in an upper punctum11 and a lower punctum 13, also referred to as punctal apertures. Thepunctal apertures are situated on a slight elevation at the medial endof the lid margin at the junction 15 of the ciliary and lacrimalportions near the medial canthus 17. The punctal apertures are round orslightly ovoid openings surrounded by a connective ring of tissue. Eachof the punctal openings 11, 13 leads into a vertical portion 10 a, 12 aof the respective canaliculus before turning horizontally to join itsother canaliculus at the entrance of a lacrimal sac 14. The canaliculaeare tubular and lined by stratified squamous epithelium surrounded byelastic tissue which permits the canaliculus to be dilated.

FIG. 1A shows a top cross sectional view of a sustained release implant100 to treat an optical defect of an eye, according to embodiments ofthe present invention. Implant 100 includes a drug core 110. Drug core110 is an implantable structure that retains a therapeutic agent. Drugcore 110 comprises a matrix 170 that contains inclusions 160 oftherapeutic agent. Inclusions 160 will often comprise a concentratedform of the therapeutic agent, for example a crystalline form of thetherapeutic agent, and the therapeutic agent may over time dissolve intomatrix 170 of drug core 110. Matrix 170 can comprise a silicone matrixor the like, and the mixture of therapeutic agent within matrix 170 canbe non-homogeneous. In many embodiments, the non-homogenous mixturecomprises a silicone matrix portion that is saturated with thetherapeutic agent and an inclusions portion comprising inclusions of thetherapeutic agent, such that the non-homogenous mixture comprises amultiphase non-homogenous mixture. In some embodiments, inclusions 160comprise droplets of an oil of the therapeutic agent, for exampleLatanoprost oil. In some embodiments, inclusions 160 may compriseparticles of the therapeutic agent, for example solid Bimatoprostparticles in crystalline form. In many embodiments, matrix 170encapsulates inclusions 160, and inclusions 160 may comprisemicroparticles have dimensions from about 1 μm to about 100 μm. Theencapsulated inclusions dissolve into the surrounding solid matrix, forexample silicone, that encapsulates the micro particles such that matrix170 is substantially saturated with the therapeutic agent while thetherapeutic agent is released from the core.

Drug core 110 is surrounded by a sheath body 120. Sheath body 120 is canbe substantially impermeable to the therapeutic agent, so that thetherapeutic agent is often released from an exposed surface on an end ofdrug core 110 that is not covered with sheath body 120. A retentionstructure 130 is connected to drug core 110 and sheath body 120.Retention structure 130 is shaped to retain the implant in a hollowtissue structure, for example, a punctum of a canaliculus as describedabove.

An occlusive element 140 is disposed on and around retention structure130. Occlusive element 140 is impermeable to tear flow and occludes thehollow tissue structure and may also serve to protect tissues of thetissue structure from retention structure 130 by providing a more benigntissue-engaging surface. Sheath body 120 includes a sheath body portion150 that connects to retention structure 130 to retain sheath body 120and drug core 110. Sheath body portion 150 can include a stop to limitmovement of sheath body 120 and drug core 110. In many embodiments,sheath body portion 150 can be formed with a bulbous tip 150B. Bulboustip 150B can comprise a convex rounded external portion that providesatraumatic entry upon introduction into the canaliculus. In manyembodiments, sheath body portion 150B can be integral with occlusiveelement 140.

FIG. 1B shows a side cross sectional view of the sustained releaseimplant of FIG. 1A. Drug core 110 is cylindrical and shown with acircular cross-section. Sheath body 120 comprises an annular portiondisposed on drug core 110. Retention structure 130 comprises severallongitudinal struts 131. Longitudinal struts 131 are connected togethernear the ends of the retention structure. Although longitudinal strutsare shown, circumferential struts can also be used. Occlusive element140 is supported by and disposed over longitudinal struts 131 ofretention structure 130 and may comprise a radially expandable membraneor the like.

FIG. 1C shows a perspective view of a sustained release implant 102 witha coil retention structure 132, according to an embodiment of thepresent invention. Retention structure 132 comprises a coil and retainsa drug core 112. A lumen, for example channel 112C, may extend throughthe drug core 112 to permit tear flow through the lumen for the deliveryof therapeutic agent for nasal and systemic applications of thetherapeutic agent. In addition or in combination with channel 112C,retention structure 132 and core 112 can be sized to permit tear flowaround the drug core and sheath body while the retention element holdstissue of the canaliculus away from the drug core. Drug core 112 may bepartially covered. The sheath body comprises a first component 122A thatcovers a first end of drug cove 112 and a second component 1228 thatcovers a second end of the drug core. An occlusive element can be placedover the retention structure and/or the retention structure can be dipcoated as described above.

FIG. 1D shows a perspective view of a sustained release implant 104 witha retention structure 134 comprising struts, according to an embodimentof the present invention. Retention structure 134 comprises longitudinalstruts and retains a drug core 114. Drug core 114 is covered with asheath body 124 over most of drug core 114. The drug core releasestherapeutic agent through an exposed end and sheath body 124 is annularover most of the drug core as described above. An occlusive element canbe placed over the retention structure or the retention structure can bedip coated as described above. A protrusion that can be engaged with aninstrument, for example a hook, a loop, a suture, or ring 124R, canextend from sheath body 124 to permit removal of the drug core andsheath body together so as to facilitate replacement of the sheath bodyand drug core while the retention structure remains implanted in thecanaliculus. In some embodiments, a protrusion that can be engaged withan instrument comprising hook, a loop, a suture or a ring, can extendfrom retention structure 134 to permit removal of the sustained releaseimplant by removing the retention structure with the protrusion, drugcore and sheath body.

FIG. 1E shows a perspective view of a sustained release implant 106 witha cage retention structure 136, according to an embodiment of thepresent invention. Retention structure 136 comprises several connectedstrands of metal and retains a drug core 116. Drug core 116 is coveredwith a sheath body 126 over most of drug core 116. The drug corereleases therapeutic agent through an exposed end and sheath body 126 isannular over most of the drug core as described above. An occlusiveelement can be placed over the retention structure or the retentionstructure can be dip coated as described above.

FIG. 1F shows a perspective view of a sustained release implantcomprising a core and sheath, according to an embodiment of the presentinvention. Drug core 118 is covered with a sheath body 128 over most ofdrug core 118. The drug core releases therapeutic agent through anexposed end and sheath body 128 is annular over most of the drug core asdescribed above.

The rate of therapeutic agent release is controlled by the surface areaof the exposed drug core and materials included within drug core 118. Inmany embodiments, the rate of elution of the therapeutic agent isstrongly and substantially related to the exposed surface area of thedrug core and weakly dependent on the concentration of drug disposed inthe inclusions in the drug core.

For circular exposed surfaces the rate of elution is strongly dependenton the diameter of the exposed surface, for example the diameter of anexposed drug core surface near an end of a cylindrical drug core. Suchan implant can be implanted in ocular tissues, for example belowconjunctival tissue layer 9 of the eye and either above sclera tissuelayer 8, as shown in FIG. 1F, or only partially within the scleraltissue layer so as not to penetrate the scleral tissue. It should benoted that drug core 118 can be used with any of the retentionstructures and occlusive elements as described herein.

In an embodiment, the drug core is implanted between sclera 8 andconjunctiva 9 without sheath body 128. In this embodiment without thesheath body, the physical characteristics of the drug core can beadjusted to compensate for the increased exposed surface of drug core,for example by reducing the concentration of dissolved therapeutic agentin the drug core matrix as described herein.

FIG. 1G schematically illustrates a sustained release implant 180comprising a flow restricting retention structure 186, a core 182 and asheath 184, according to an embodiment of the present invention. Sheathbody 184 can at least partially cover drug core 182. Drug core 182 maycontain inclusions of the therapeutic agent therein to provide asustained release of the therapeutic agent. Drug core 182 can include anexposed convex surface area 182A. Exposed convex surface area 182A mayprovide an increased surface area to release the therapeutic agent.

An occlusive element 188 can be disposed over retention structure 186 toblock the flow of tear through the canaliculus. In many embodiments,retention structure 186 can be located within occlusive structure 188 toprovide the occlusive element integrated with the retention structure.

Flow restricting retention structure 186 and occlusive element 188 canbe sized to block tear flow through the canaliculus.

The cores and sheath bodies described herein can be implanted in avariety of tissues in several ways. Many of the cores and sheathsdescribed herein, in particular the structures described with referenceto FIGS. 2A to 2J can be implanted alone as punctal plugs.

Alternatively, many of the cores and sheath bodies described herein cancomprise a drug core, sheath body, and/or the like so as to be implantedwith the retention structures and occlusive elements described herein.

FIG. 2A shows a cross sectional view of a sustained release implant 200with core comprising an enlarged exposed surface area, according to anembodiment of the present invention. A drug core 210 is covered with asheath body 220. Sheath body 220 includes an opening 220A. Opening 220has a diameter that approximates the maximum cross sectional diameter ofdrug core 210. Drug core 210 includes an exposed surface 210E, alsoreferred to as an active surface. Exposed surface 210E includes 3surfaces: an annular surface 210A, a cylindrical surface 210B and an endsurface 210C. Annular surface 210A has an outer diameter thatapproximates the maximum cross sectional diameter of core 210 and aninner diameter that approximates the outer diameter of cylindricalsurface 210B. End surface 210C has a diameter that matches the diameterof cylindrical surface 210B. The surface area of exposed surface 210E isthe sum of the areas of annular surface 210A, cylindrical surface 210Band end surface 210C.

The surface area may be increased by the size of cylindrical surfacearea 210B that extends longitudinally along an axis of core 210.

FIG. 2B shows a cross sectional view of a sustained release implant 202with a core 212 comprising an enlarged exposed surface area 212A,according to an embodiment of the present invention. A sheath body 222extends over core 212. The treatment agent can be released from the coreas described above. Exposed surface area 212A is approximately conical,can be ellipsoidal or spherical, and extends outward from the sheathbody to increase the exposed surface area of drug core 212.

FIGS. 2C and 2D show perspective and cross sectional views,respectively, of a sustained release implant 204 with a drug core 214comprising a reduced exposed surface area 214A, according to anembodiment of the present invention. Drug core 214 is enclosed within asheath body 224. Sheath body 22 includes an annular end portion 224Athat defines an opening through which drug core 214 extends. Drug core214 includes an exposed surface 214A that releases the therapeuticagent. Exposed surface 214A has a diameter 214D that is less than amaximum dimension, for example a maximum diameter, across drug core 214.

FIG. 2E shows a cross sectional view of a sustained release implant 206with a drug core 216 comprising an enlarged exposed surface area 216Awith castellation extending therefrom, according to an embodiment of thepresent invention. The castellation includes several spaced apartfingers 216F to provide increased surface area of the exposed surface216A.

In addition to increased surface area provided by castellation, drugcore 216 may also include an indentation 2161. Indentation 2161 may havethe shape of an inverted cone. Core 216 is covered with a sheath body226. Sheath body 226 is open on one end to provide an exposed surface216A on drug core 216. Sheath body 226 also includes fingers and has acastellation pattern that matches core 216.

FIG. 2F shows a perspective view of a sustained release implant 250comprising a core with folds, according to an embodiment of the presentinvention. Implant 250 includes a core 260 and a sheath body 270. Core260 has an exposed surface 260A on the end of the core that permits drugmigration to the surrounding tear or tear film fluid. Core 260 alsoincludes folds 260F. Folds 260F increase the surface area of core thatis exposed to the surrounding fluid tear or tear film fluid. With thisincrease in exposed surface area, folds 260F increase migration of thetherapeutic agent from core 260 into the tear or tear film fluid andtarget treatment area.

Folds 260F are formed so that a channel 260C is formed in core 260.Channel 260C connects to the end of the core to an opening in exposedsurface 260A and provides for the migration of treatment agent. Thus,the total exposed surface area of core 260 includes exposed surface 260Athat is directly exposed to the tear or tear film fluid and the surfacesof folds 260F that are exposed to the tear or tear film fluids viaconnection of channel 260C with exposed surface 260A and the tear ortear film fluid.

FIG. 2G shows a perspective view of a sustained release implant with acore comprising a channel with an internal porous surface, according toan embodiment of the present invention.

Implant 252 includes a core 262 and sheath body 272. Core 262 has anexposed surface 262A on the end of the core that permits drug migrationto the surrounding tear or tear film fluid. Core 262 also includes achannel 262C. Channel 262C increases the surface area of the channelwith a porous internal surface 262P formed on the inside of the channelagainst the core. Channel 262C extends to the end of the core nearexposed surface 262A of the core. The surface area of core that isexposed to the surrounding tear or tear film fluid can include theinside of core 262 that is exposed to channel 262C. This increase inexposed surface area can increase migration of the therapeutic agentfrom core 262 into the tear or tear film fluid and target treatmentarea. Thus, the total exposed surface area of core 262 can includeexposed surface 260A that is directly exposed to the tear or tear filmfluid and porous internal surface 262P that is exposed to the tear ortear film fluids via connection of channel 262C with exposed surface262A and the tear or tear film fluid.

FIG. 2H shows a perspective view of a sustained release implant 254 witha core 264 comprising channels to increase drug migration, according toan embodiment of the invention. Implant 254 includes core 264 and sheathbody 274. Exposed surface 264A is located on the end of core 264,although the exposed surface can be positioned at other locations.Exposed surface 264A permits drug migration to the surrounding tear ortear film fluid. Core 264 also includes channels 264C Channels 264Cextend to exposed surface 264. Channels 264C are large enough that tearor tear film fluid can enter the channels and therefore increase thesurface area of core 264 that is in contact with tear or tear filmfluid. The surface area of the core that is exposed to the surroundingfluid tear or tear film fluid includes the inner surfaces 264P of core262 that define channels 264C. With this increase in exposed surfacearea, channels 264C increase migration of the therapeutic agent fromcore 264 into the tear or tear film fluid and target treatment area.Thus, the total exposed surface area of core 264 includes exposedsurface 264A that is directly exposed to the tear or tear film fluid andinternal surface 264P that is exposed to the tear or tear film fluidsvia connection of channels 262C with exposed surface 264A and the tearor tear film fluid.

FIG. 2I shows a perspective view of a sustained release implant 256 witha drug core 266 comprising a convex exposed surface 266A, according toan embodiment of the present invention. Drug core 266 is partiallycovered with a sheath body 276 that extends at least partially over drugcore 266 to define convex exposed surface 266A. Sheath body 276comprises a shaft portion 276S. Convex exposed surface 266A provides anincreased exposed surface area above the sheath body. A cross sectionalarea of convex exposed surface 266A is larger than a cross sectionalarea of shaft portion 276S of sheath body 276. In addition to the largercross sectional area, convex exposed surface 266A has a larger surfacearea due to the convex shape which extends outward from the core. Sheathbody 276 comprises several fingers 276F that support drug core 266 inthe sheath body and provide support to the drug core to hold drug core266 in place in sheath body 276. Fingers 276F are spaced apart to permitdrug migration from the core to the tear or tear film fluid between thefingers. Protrusions 276P extend outward on sheath body 276. Protrusions276P can be pressed inward to eject drug core 266 from sheath body 276.Drug core 266 can be replaced with another drug core after anappropriate time, for example after drug core 266 has released most ofthe therapeutic agent.

FIG. 2J shows a side view of a sustained release implant 258 with a core268 comprising an exposed surface area with several soft brush-likemembers 268F, according to an embodiment of the present invention. Drugcore 268 is partially covered with a sheath body 278 that extends atleast partially over drug core 268 to define exposed surface 268A.Sheath body 278 comprises a shaft portion 278S. Soft brush-like members268F extend outward from drug core 268 and provide an increased exposedsurface area to drug core 268. Soft brush-like members 268F are alsosoft and resilient and easily deflected such that these members do notcause irritation to neighboring tissue. Although drug core 268 can bemade of many materials as explained above, silicone is a suitablematerial for the manufacture of drug core 268 comprises soft brush likemembers 268F. Exposed surface 268A of drug core 268 also includes anindentation 2681 such that at least a portion of exposed surface 268A isconcave.

FIG. 2K shows a side view of a sustained release implant 259 with a drugcore 269 comprising a convex exposed surface 269A, according to anembodiment of the present invention. Drug core 269 is partially coveredwith a sheath body 279 that extends at least partially over drug core269 to define convex exposed surface 269A. Sheath body 279 comprises ashaft portion 279S. Convex exposed surface 269 provides an increasedexposed surface area above the sheath body. A cross sectional area ofconvex exposed surface 269A is larger than a cross sectional area ofshaft portion 279S of sheath body 279. In addition to the larger crosssectional area, convex exposed surface 269A has a larger surface areadue to the convex shape that extends outward on the core. A retentionstructure 289 can be attached to sheath body 279. Retention structure289 can comprise any of the retention structures as describe herein, forexample a coil comprising a super elastic shape memory alloy such asNITANOL®. Retention structure 289 can be dip coated to make retentionstructure 289 biocompatible.

FIG. 2L shows a side view of a sustained release implant 230 with a drugcore 232 comprising a concave indented surface 232A to increase exposedsurface area of the core, according to an embodiment of the presentinvention. A sheath body 234 extends at least partially over drug core232. Concave indented surface 232A is formed on an exposed end of drugcore 232 to provide an increased exposed surface area of the drug core.

FIG. 2M shows a side view of a sustained release implant 240 with a drugcore 242 comprising a concave surface 242A with a channel 242C formedtherein to increase an exposed surface area of the core, according to anembodiment of the present invention. A sheath body 244 extends at leastpartially over drug core 242. Concave indented surface 242A is formed onan exposed end of drug core 232 to provide an increased exposed surfacearea of the drug core. Channel 242C formed in drug core 242 to providean increased exposed surface area of the drug core. Channel 242C canextend to concave indented surface 242A such that channel 242C andprovide an increase in surface area of the core exposed to the tear ortear film.

FIG. 3A shows an implant 310 comprising a sheath body 320 withextensions 322, according to an embodiment of the present invention.Extensions 322 attach sheath body 320 to the retention element to retainthe core near the punctum. Sheath body 320 extends over core 330 todefine an exposed surface 332 of core 330. Extensions 322 can beresilient and engage the retention element and/or occlusive element toattach the sheath body core to the retention element to retain the corenear the punctum.

FIG. 3B shows an implant 350 comprising a retention element 380 with anextension 382, according to an embodiment of the present invention.Extension 382 retains a sheath body 360 and a core 370. Sheath body 360extends over core 370 to define an exposed surface 372 of core 370.Exposed surface 372 is disposed near the proximal end of core 370.Extension 382 extends downward to retain core 370 and sheath body 370.

FIGS. 4A and 4B show a cross-sectional view of an implant 400 with aretention structure 430 that is shorter in length while in a largecross-sectional profile configuration than a small cross-sectionalprofile configuration, according to an embodiment of the presentinvention. Implant 400 includes a distal end 402 and a proximal end 404.Implant 400 includes a drug core 410 and a sheath body 420. Sheath body420 at least partially covers drug core 410 and defines an exposedsurface 412 of drug core 410. An occlusive element 440 can be attachedto and supported by retention structure 430. Occlusive element 440 canmove with retention structure 430, for example when retention element430 expands from a small profile configuration to a large profileconfiguration. In many embodiments, the retention structure andocclusive element are sized to correspond to a diameter of thecanaliculus, for example to match a diameter of the canaliculus orslightly larger than the canalicular diameter, so as occlude fluid flowthrough the canaliculus and/or anchor in the canaliculus.

As shown in FIG. 4A, retention structure 430 and occlusive element 440are in a small profile configuration. Such a small profile configurationcan occur while the occlusive element and retention structure are placedin a tip of an insertion tool and covered for deployment. Retentionelement 430 and occlusive element 440 extend fully along the length ofsheath body 420 and drug core 410. Retention element 430 is attached tosheath body 420 near distal end 402. In many embodiments, retentionstructure 430 and occlusive element 440 have diameters that are sized tofit inside and slide within the canaliculus while in the small profileconfiguration, and the retention structure and occlusive element can besized to anchor within the canaliculus while in a second large profileconfiguration.

As shown in FIG. 4B, retention structure 430 and occlusive element 440are in a large profile configuration. Such a large profile configurationcan occur when the occlusive element and retention structure are placedin the canaliculus. In the large profile configuration, the length ofocclusive element 440 and retention structure 430 is shorter than in thesmall profile configuration by a distance 450. The proximal end ofretention structure 430 and occlusive element 440 can slide over sheathbody 420 when the sheath body and retention structure assume the largeprofile configuration such that the proximal end of drug core 410 andsheath body 420 extend from the retention structure and occlusiveelement. In some embodiments, the sheath body is shorter than drug core410 by distance 450 so that more of the drug core is exposed while theretention structure and occlusive element are in the large profileconfiguration than is exposed while the retention structure andocclusive element are in the small profile configuration. In suchembodiments, the retention structure and occlusive element retract toexpose the drug core.

FIGS. 5A to 6 show embodiments of tools that can be used to insert manyof the implants as describe herein.

FIG. 5A shows an insertion tool 500 to insert an implant into thepunctum with a plunger 530 that can be depressed, according to anembodiment of the present invention. Insertion tool 500 includes adilator 510 that can be inserted into the punctum to pre-dilate thepunctum prior to insertion of an implant. An implant 520 can bepre-loaded onto tool 500 prior to dilation of the punctum. An internalwire 540 can be connected to implant 520 to retain the implant.Following pre-dilation of the punctum with dilator 510, tool 500 can beused to insert implant 520 into the punctum. While implant 520 ispositioned in the punctum, plunger 530 can be depressed to engage wire540 and release implant 520 from tool 500.

FIG. 5B shows an insertion tool 550 to insert an implant 570 into thepunctum with a plunger that can slide, according to an embodiment of thepresent invention. Insertion tool 550 includes a dilator 560 with aconical section to dilate the punctum. Implant 550 includes a plunger580 that can slide distally to advance implant 570 into the lumen. Ashaft 590 is connected to plunger 580 to advance implant 570 distallywhen plunger 580 is advanced distally. While the punctum is dilated withdilator 560, plunger 580 can be advanced distally to place implant 570in the canalicular lumen near the punctum. In many embodiments, a buttoncan be depressed to advance distally the implant into the lumen, forexample a button connected to shaft 590 with an intermediate mechanism.

FIG. 6 shows an insertion tool 600 to insert an implant into the punctumwith a sheath 610 that retracts to position the implant in thecanalicular lumen, according to an embodiment of the present invention.At least a portion of sheath 610 is shaped to dilate the punctum. Sheath610 is shaped to hold an implant 620 in a small profile configuration.Insertion tool 600 includes an annular structure 615, which can comprisea portion of a body 605 of insertion tool 600. Sheath 610 and annularstructure 615 are shaped to dilate the punctum and often compriseproximally inclined surfaces to dilate the punctum. Implant 620, sheath610 and annular structure 615 can be at least partially inserted intothe punctum to place the implant in the canalicular lumen. Annularstructure 615 is disposed over sheath 610 so that sheath 610 can beretracted and slide under annular structure 615. A stop 625 can beconnected to body 605 to retain implant 620 at the desired depth withinthe canalicular lumen while sheath 610 is retracted proximally to exposeimplant 620.

Once implant 620 has been positioned in the canalicular lumen at thedesired depth in relation to the punctum, sheath 610 is retracted toexpose implant 620 at the desired location in the canalicular lumen. Aplunger 630 can be used to retract sheath 610. A shaft 640 mechanicallycouples sheath 610 to plunger 630. Thus, retraction of plunger 630 inthe proximal direction can retract sheath 610 in the proximal directionto expose implant 620 at the desired location in the canalicular lumen.Implant 620 can be any of the implants as described herein. Often,implant 620 will comprise a resilient member that expands to a largeprofile configuration when sheath 610 is retracted. In many embodiments,insertion tool 600 can include a dilator to dilate the punctum prior toinsertion of the implant, and the dilator can be positioned on an end ofthe insertion tool that opposes the end loaded with the implant, asdescribed herein above.

FIGS. 5A to 5C schematically illustrate replacement of a drug core 510and a sheath body 520, according to an embodiment of the presentinvention. An implant 700 comprises drug core 510, sheath body 520 and aretention structure 530. Implant 500 can include an occlusive elementsupport by and movable with retention structure 530. Often retentionstructure 530 can assume a first small profile configuration prior toimplantation and a second large profile configuration while implanted.Retention structure 530 is shown in the large profile configuration andimplanted in the canalicular lumen. Sheath body 520 includes extension525A and extension 525B to attach the sheath body and drug core toretention structure 530 so that the sheath body and drug core areretained by retention structure 530. Drug core 510 and sheath body 520can be removed together by drawing drug core 510 proximally as shown byarrow 530. Retention structure 530 can remain implanted in thecanalicular tissue after drug core 510 and sheath body 520 have beenremoved as shown in FIG. 5B. A replacement core 560 and replacementsheath body 570 can be inserted together as shown in FIG. 5C. Suchreplacement can be desirable after drug core 510 has released effectiveamounts of therapeutic agent such that the supply of therapeutic agentin the drug core has diminished and the rate of therapeutic agentreleased is near the minimum effective level. Replacement sheath body570 includes extension 575A and extension 575B. Replacement drug core560 and replacement sheath body 570 can be advanced distally as shown byarrow 590 to insert replacement drug core 560 and replacement sheathbody 570 into retention structure 530. Retention structure 530 remainsat substantially the same location while replacement drug core 560 andreplacement sheath body 570 are inserted into resilient member 530.

FIGS. 6A to 6C show deployment of a sustained release implant, accordingto an embodiment of the present invention. As shown in FIG. 6A, adeployment instrument 610 is inserted into a canaliculus 600 through apunctum 600A. A sustained release implant 620 is loaded into a tip ofdeployment instrument 610, and a sheath 612 covers sustained releaseimplant 620. Retention structure 630 assumes a small profileconfiguration while sheath 612 is positioned over retention structure630. As shown in FIG. 6B, outer sheath 612 of deployment instrument 610is withdrawn to expose a retention structure 630 of sustained releaseimplant 620. The exposed portion of retention element 630 assumes alarge profile configuration. As shown in FIG. 6C, deployment instrument610 has been removed and sustained release implant 620 is implanted incanaliculus 600. A drug core 640 is attached retention structure 630 andretained in the canaliculus. An outer body sheath 650 covers at least aportion of drug core 640 and drug core 640 releases a therapeutic agentinto a liquid tear or tear film 660 near punctum 600A of canaliculus600.

Sheath Body

The sheath body comprises appropriate shapes and materials to controlmigration of the therapeutic agent from the drug core. The sheath bodyhouses the core and can fit snugly against the core. The sheath body ismade from a material that is substantially impermeable to thetherapeutic agent so that the rate of migration of the therapeutic agentmay be largely controlled by the exposed surface area of the drug corethat is not covered by the sheath body. In many embodiments, migrationof the therapeutic agent through the sheath body can be about one tenthof the migration of the therapeutic agent through the exposed surface ofthe drug core, or less, often being one hundredth or less. In otherwords, the migration of the therapeutic agent through the sheath body isat least about an order of magnitude less that the migration of thetherapeutic agent through the exposed surface of the drug core. Suitablesheath body materials include polyimide, polyethylene terephthalate”(hereinafter “PET”). The sheath body has a thickness, as defined fromthe sheath surface adjacent the core to the opposing sheath surface awayfrom the core, from about 0.00025″ to about 0.0015″. The total diameterof the sheath that extends across the core ranges from about 0.2 mm toabout 1.2 mm. The core may be formed by dip coating the core in thesheath material. Alternatively or in combination, the sheath body cancomprise a tube and the core introduced into the sheath, for example asa liquid or solid that can be slid, injected and/or extruded into thesheath body tube. The sheath body can also be dip coated around thecore, for example dip coated around a pre-formed core.

The sheath body can be provided with additional features to facilitateclinical use of the implant. For example, the sheath may receive a drugcore that is exchangeable while the retention structure and sheath bodyremain implanted in the patient. The sheath body is often rigidlyattached to the retention structure as described above, and the core isexchangeable while the retention structure retains the sheath body. Inspecific embodiments, the sheath body can be provided with externalprotrusions that apply force to the sheath body when squeezed and ejectthe core from the sheath body. Another drug core can then be positionedin the sheath body. In many embodiments, the sheath body and/orretention structure may have a distinguishing feature, for example adistinguishing color, to show placement such that the placement of thesheath body and/or retention structure in the canaliculus or other bodytissue structure can be readily detected by the patient. The retentionelement and/or sheath body may comprise at least one mark to indicatethe depth of placement in the canaliculus such that the retentionelement and/or sheath body can be positioned to a desired depth in thecanaliculus based on the at least one mark.

Retention Structure

The retention structure comprises an appropriate material that is sizedand shaped so that the implant can be easily positioned in the desiredtissue location, for example the canaliculus. The retention structure ismechanically deployable and typically expands to a desired crosssectional shape, for example with the retention structure comprising asuper elastic shape memory alloy such as NITANOL®. Other materials inaddition to NITANOL® can be used, for example resilient metals orpolymers, plastically deformable metals or polymers, shape memorypolymers, and the like, to provide the desired expansion. In someembodiments polymers and coated fibers available from Biogeneral, Inc.of San Diego, Calif. may be used. Many metals such as stainless steelsand non-shape memory alloys can be used and provide the desiredexpansion. This expansion capability permits the implant to fit inhollow tissue structures of varying sizes, for example canaliculacranging from 0.3 mm to 1.2 mm (i.e. one size fits all).

Although a single retention structure can be made to fit canaliculaefrom 0.3 to 1.2 mm across, a plurality of alternatively selectableretention structures can be used to fit this range if desired, forexample a first retention structure for canaliculae from 0.3 to about0.9 mm and a second retention structure for canaliculae from about 0.9to 1.2 mm The retention structure has a length appropriate to theanatomical structure to which the retention structure attaches, forexample a length of about 3 mm for a retention structure positioned nearthe punctum of the canaliculus. For different anatomical structures, thelength can be appropriate to provide adequate retention force, e.g. 1 mmto 15 mm lengths as appropriate.

Although the sheath body and drug core are attached to one end of theretention structure as described above, in many embodiments the otherend of retention structure is not attached to drug core and sheath bodyso that the retention structure can slide over the sheath body and drugcore while the retention structure expands. This sliding capability onone end is desirable as the retention structure may shrink in length asthe retention structure expands in width to assume the desired crosssectional width. However, it should be noted that many embodiments mayemploy a sheath body that does not slide in relative to the core.

In many embodiments, the retention structure can be retrieved fromtissue. A protrusion, for example a hook, a loop, or a ring, can extendfrom the retention structure to facilitate removal of the retentionstructure.

Occlusive Element

The occlusive element comprises an appropriate material that is sizedand shaped so that the implant can at least partially inhibit, evenblock, the flow of fluid through the hollow tissue structure, forexample lacrimal fluid through the canaliculus. The occlusive materialshown is a thin walled membrane of a biocompatible material, for examplesilicone, that can expand and contract with the retention structure. Theocclusive element is formed as a separate thin tube of material that isslid over the end of the retention structure and anchored to one end ofthe retention structure as described above. Alternatively, the occlusiveelement can be formed by dip coating the retention structure in abiocompatible polymer, for example silicone polymer. The thickness ofthe occlusive element can be in a range from about 0.01 mm to about 0.15mm, and often from about 0.05 mm to 0.1 mm.

Therapeutic Agents

A “therapeutic agent” can comprise a drug may be any of the following ortheir equivalents, derivatives or analogs, including, anti-glaucomamedications, (e.g. adrenergic agonists, adrenergic antagonists (betablockers), carbonic anhydrase inhibitors (CAIS, systemic and topical),parasympathomimetics, prostaglandins and hypotensive lipids, andcombinations thereof), antimicrobial agent (e.g., antibiotic, antiviral,antiparacytic, antifungal, etc.), a coiticosteroid or otheranti-inflammatory (e.g., an NSAID), a decongestant (e.g.,vasoconstrictor), an agent that prevents of modifies an allergicresponse (e.g., an antihistamine, cytokine inhibitor, leucotrieneinhibitor, IgE inhibitor, immunomodulator), a mast cell stabilizer,cycloplegic or the like. Examples of conditions that may be treated withthe therapeutic agent(s) include but are not limited to glaucoma, preand post surgical treatments, dry eye and allergies. In someembodiments, the therapeutic agent may be a lubricant or a surfactant,for example a lubricant to treat dry eye.

Exemplary therapeutic agents include, but are not limited to, thrombininhibitors; antithrombogenic agents; thrombolytic agents; fibrinolyticagents; vasospasm inhibitors; vasodilators; antihypertensive agents;antimicrobial agents, such as antibiotics (such as tetracycline,chlortetracycline, bacitracin, neomycin, polymyxin, gramicidin,cephalexin, oxytetracycline, chloramphenicol, rifampicin, ciprofloxacin,tobramycin, gentamycin, erythromycin, penicillin, sulfonamides,sulfadiazine, sulfacetamide, sulfamethizole, sulfisoxazole,nitrofurazone, sodium propionate), antifungals (such as amphotericin Band miconazole), and antivirals (such as idoxuridine trifluorothymidine,acyclovir, gancyclovir, interferon); inhibitors of surface glycoproteinreceptors; antiplatelet agents; antimitotics; microtubule inhibitors;anti-secretory agents; active inhibitors; remodeling inhibitors;antisense nucleotides; anti-metabolites; antiproliferatives (includingantiangiogenesis agents); anticancer chemotherapeutic agents;anti-inflammatories (such as hydrocortisone, hydrocortisone acetate,dexamethasone 21-phosphate, fluocinolone, medrysone, methylprednisolone,prednisolone 21-phosphate, prednisolone acetate, fluoromethalone,betamethasone, triamcinolone, triamcinolone acetonide); non steroidalanti-inflammatories (NSAIDs) (such as salicylate, indomethacin,ibuprofen, diclofenac, flurbiprofen, piroxicam indomethacin, ibuprofen,naxopren, piroxicam and nabumetone). Such anti inflammatory steroidscontemplated for use in the methodology of the present invention,include triamcinolone acetonide (generic name) and corticosteroids thatinclude, for example, triamcinolone, dexamethasone, fluocinolone,cortisone, prednisolone, flumetholone, and derivatives thereof);antiallergenics (such as sodium chromoglycate, antazoline,methapyriline, chlorpheniramine, cetrizine, pyrilamine,prophenpyridamine); anti proliferative agents (such as 1,3-cis retinoicacid, 5-fluorouracil, taxol, rapamycin, mitomycin C and cisplatin);decongestants (such as phenylephrine, naphazoline, tetrahydrazoline);miotics and anti-cholinesterase (such as pilocarpine, salicylate,carbachol, acetylcholine chloride, physostigmine, eserine, diisopropylfluorophosphate, phospholine iodine, demecarium bromide);antineoplastics (such as carmustine, cisplatin, fluorouracil3;immunological drugs (such as vaccines and immune stimulants); hormonalagents (such as estrogens, —estradiol, progestational, progesterone,insulin, calcitonin, parathyroid hormone, peptide and vasopressinhypothalamus releasing factor); immunosuppressive agents, growth hormoneantagonists, growth factors (such as epidermal growth factor, fibroblastgrowth factor, platelet derived growth factor, transforming growthfactor beta, somatotrapin, fibronectin); inhibitors of angiogenesis(such as angiostatin, anecortave acetate, thrombospondin, anti-VEGFantibody); dopamine agonists; radiotherapeutic agents; peptides;proteins; enzymes; extracellular matrix; components; ACE inhibitors;free radical scavengers; chelators; antioxidants; anti polymerases;photodynamic therapy agents; gene therapy agents; and other therapeuticagents such as prostaglandins, antiprostaglandins, prostaglandinprecursors, including antiglaucoma drugs including beta-blockers such asTimolol, betaxolol, levobunolol, atenolol, and prostaglandin analoguessuch as Bimatoprost, travoprost, Latanoprost etc; carbonic anhydraseinhibitors such as acetazolamide, dorzolamide, brinzolamide,methazolamide, dichlorphenamide, diamox; and neuroprotectants such aslubezole, nimodipine and related compounds; and parasympathomimetricssuch as pilocarpine, carbachol, physostigmine and the like.

The amount of drug associated with the drug-delivery device may varydepending on the particular agent, the desired therapeutic benefit andthe time during which the device is intended to deliver the therapy.Since the devices of the present invention present a variety of shapes,sizes and delivery mechanisms, the amount of drug associated with thedevice will depend on the particular disease or condition to be treated,and the dosage and duration that is desired to achieve the therapeuticeffect. Generally, the amount of drug is at least the amount of drugthat upon release from the device, is effective to achieve the desiredphysiological or pharmacological local or systemic effects.

Embodiments of the drug delivery devices of the present invention can beadapted to provide delivery of drug at a daily rate that issubstantially below the therapeutically effective drop form of treatmentso as to provide a large therapeutic range with a wide safety margin.For example, many embodiments treat the eye with therapeutic levels forextended periods that are no more than 5 or 10 percent of the daily dropdosage. Consequently, during an initial bolus or washout period of aboutone to three days, the implant can elute the therapeutic agent at a ratethat is substantially higher than the sustained release levels and wellbelow the daily drop form dosage. For example, with an average sustainedrelease level of 100 ng per day, and an initial release rate of 1000 to1500 ng per day, the amount of drug initially released is less than the2500 ng of drug that may be present in a drop of drug delivered to theeye. This used use of sustained release levels substantially below theamount of drug in a drop and/or drops administered daily allows thedevice to release a therapeutically beneficial amount of drug to achievethe desired therapeutic benefit with a wide safety margin, whileavoiding an inadequate or excessive amount of drug at the intended siteor region.

An extended period of time may mean a relatively short period of time,for example minutes or hours (such as with the use of an anesthetic),through days or weeks (such as the use of pre-surgical or post-surgicalantibiotics, steroids, or NSAIDs and the like), or longer (such as inthe case of glaucoma treatments), for example months or years (on arecurring basis of use of the device).

For example, a drug such as Timolol maleate, a beta1 and beta2(non-selective) adrenergic receptor blocking agent can be used in thedevice for a release over an extended period of time such as 3 months.Three months is a relatively typical elapsed time between physicianvisits for a glaucoma patient undergoing topical drop therapy with aglaucoma drug, although the device could provide treatment for longer orshorter durations. In the three month example, a 0.25% concentration ofTimolol translates to from 2.5 to 5 mg/1000 μL, typically being 2.5 mg/1000 μL A drop of Timolol for topical application is usually in the rangeof 40-60 μL, typically being 50 μL. Thus, there may be 0.08-0.15 mg,typically being 0.125 mg of Timolol in a drop. There may beapproximately 8% (optionally 6-10%) of the drop left in the eye after 5minutes, so about 10 .mu·g of the drug is available at that time.Timolol may have a bioavailability of 30-50%, which means that from 1.5to 7.5 μg, for example 4 μg of the drug is available to the eye. Timololis generally applied twice a day, so 8 (or 3-15) μg is available to theeye each day. Therefore, a delivery device might contain from 270 to1350 for example 720 μg, of the drug for a 90 day, or 3 month, extendedrelease. The drug would be contained within the device and eluted basedon the polymer or drug/hydrogel concentration. The drug can be similarlycontained on the device and eluted for olopatadine hydrochloride(PATANOL®) and other drugs in a manner similar to Timolol.

Commercially available solutions of Timolol maleate are available in0.25% and 0.5% preparations, and the initial dosage can be 1 drop twiceper day of 0.25% solution. A 0.25% concentration of Timolol isequivalent to 2.5 mg per 1000 μl. A sustained release quantity ofTimolol released each day from the drug core can be from about 3 to 15μg each day. Although the sustained release quantity delivered each dayfrom the device may vary, a sustained release delivery of about 8 μg perday corresponds to about 3.2% of the 0.250 mg of Timolol applied withtwo drops of a 0.25% solution.

For example, in the case of Latanoprost (Xalatan), a prostaglandin F2αanalogue, this glaucoma medication has concentrations that are about1/10^(th) that of Timolol. Therefore, the amount of drug on theimplantable device, depending on the bioavailability, would besignificantly less—approximately 20-135 μg and typically 50-100 μg—forLatanoprost and other prostaglandin analogues. This also translates to adevice that can either be smaller than one required for a beta blockerdelivery or can house more drug for a longer release period.

A drop of Xalatan contains about 2.5 μg of Latanoprost, assuming a 50 μLdrop volume. Therefore, assuming that about 8% of 2.5 μg is present 5minutes after instillation, only about 200 ng of drug remains on theeye. Based on the Latanoprost clinical trials, this amount is effectivein lowering IOP for at least 24 hours. Pfizer/Pharmacia conductedseveral dose-response studies in support of the NDA for Xalatan. Thedoses ranged from 12.5 μg/mL to 115 μ/mL of Latanoprost. The currentdose of Latanoprost, 50 μg/mL, given once per day, was shown to beoptimal. However, even the lowest doses of 12.5 μg/mL QD or 15 μg/mL BIDconsistently gave about 60-75% of the IOP reduction of the 50 μg/mL QDdose. Based on the assumptions above, a 12.5 μg/mL concentrationprovides 0.625 μg of Latanoprost in a 50 μL drop, which results in onlyabout 50 ng (8%) of drug remaining in the eye after 5 minutes.

In many embodiments, the concentrations of Latanoprost are about1/100^(th), or 1 percent, that of Timolol, and in specific embodimentsthe concentrations of Latanoprost may be about 1/50^(th), or 2 percent,that of Timolol. For example, commercially available solutionpreparations of Latanoprost are available at concentrations 0.005%,often delivered with one drop per day. In many embodiments, thetherapeutically effective concentration of drug released from the deviceper day can be about 1/100^(th) of Timolol, about 30 to 150 ng per day,for example about 80 ng, assuming tear washout and bioavailabilitysimilar to Timolol. For example, the amount of drug on the implantabledevice, can be significantly less—approximately 1% to 2% of Timolol, forexample 2.7 to 13.5 μg, and can also be about 3 to 20 μg, forLatanoprost and other prostaglandin analogues. Although the sustainedrelease amount of Latanoprost released each day can vary, a sustainedrelease of 80 ng per day corresponds to about 3.2% of the 2.5 μg ofLatanoprost applied with a single drop of a 0.005% solution.

For example, in the case of Bimatoprost (Lumigan), a syntheticprostamide prostaglandin analogue, this glaucoma medication may haveconcentrations that are 1/20^(th) or less than that of Timolol.Therefore, the amount of drug loaded on the extended release device fora 3 to 6 month extended release, depending on the bioavailability, canbe significantly less, approximately 5-30 μg and typically 10-20 μg—forBimatoprost and analogues and derivatives thereof. In many embodiments,the implant can house more drug for a longer sustained release period,for example 20-40 μg for a sustained release period of 6 to 12 monthswith Bimatoprost and its derivatives. This decrease in drugconcentration can also translate to a device that can be smaller thanone required for a beta blocker delivery.

Commercially available solution concentrations of Bimatoprost are 0.03%by weight, often delivered once per day. Although the sustained releaseamount of Bimatoprost released each day can vary, a sustained release of300 ng per day corresponds to about 2% of the 15 μg of Bimatoprostapplied with a single drop of a 0.03% solution. Work in relation withthe present invention suggests that even lower sustained release dosesof Bimatoprost can provide at least some reduction in intraocularpressure, for example 20 to 200 ng of Bimatoprost and daily sustainedrelease dosages of 0.2 to 2% of the daily drop dosage.

For example, in the case of Travoprost (Travatan), a prostaglandinF2.alpha. analogue, this glaucoma medication may have concentrationsthat are 2% or less than that of Timolol. For example, commerciallyavailable solution concentrations are 0.004%, often delivered once perday. In many embodiments, the therapeutically effective concentration ofdrug released from the device per day can be about 65 ng, assuming tearwashout and bioavailability similar to Timolol. Therefore, the amount ofdrug on the implantable device, depending on the bioavailability, wouldbe significantly less. This also translates to a device that can eitherbe smaller than one required for a beta blocker delivery or can housemore drug for a longer release period. For example, the amount of drugon the implantable device, can be significantly less—approximately 1/100of Timolol, for example 2.7 to 13.5 μg, and typically about 3 to 20 μg,for Travoprost, Latanoprost and other prostaglandin F2α analogues.Although the sustained release amount of Latanoprost released each daycan vary, a sustained release of 65 ng per day corresponds to about 3.2%of the 2.0 μg of Travoprost applied with a single drop of a 0.004%solution.

In some embodiments, the therapeutic agent may comprise a corticosteroid, for example fluocinolone acetonide, to treat a target oculartissue. In specific embodiments, fluocinolone acetonide can be releasedfrom the canaliculus and delivered to the retina as a treatment fordiabetic macular edema (DME).

It is also within the scope of this invention to modify or adapt thedevices to deliver a high release rate, a low release rate, a bolusrelease, a burst release, or combinations thereof. A bolus of the drugmay be released by the formation of an erodable polymer cap that isimmediately dissolved in the tear or tear film. As the polymer cap comesin contact with the tear or tear film, the solubility properties of thepolymer enable the cap to erode and the drug is released all at once. Aburst release of a drug can be performed using a polymer that alsoerodes in the tear or tear film based on the polymer solubility. In thisexample, the drug and polymer may be stratified along the length of thedevice so that as the outer polymer layer dissolves, the drug isimmediately released. A high or low release rate of the drug could beaccomplished by changing the solubility of the erodable polymer layer sothat the drug layer released quickly or slowly. Other methods to releasethe drug could be achieved through porous membranes, soluble gels (suchas those in typical ophthalmic solutions), microparticle encapsulationsof the drug, or nanoparticle encapsulation, depending on the size of thedrug molecule.

Drug Core

The drug core comprises the therapeutic agent and materials to providesustained release of the therapeutic agent. The therapeutic agentmigrates from the drug core to the target tissue, for example ciliarymuscles of the eye. The therapeutic agent may optionally be onlyslightly soluble in the matrix so that a small amount of therapeuticagent is dissolved in the matrix and available for release from thesurface of drug core 110. As the therapeutic agent diffuses from theexposed surface of the core to the tear or tear film, the rate ofmigration from the core to the tear or tear film can be related to theconcentration of therapeutic agent dissolved in the matrix. In additionor in combination, the rate of migration of therapeutic agent from thecore to the tear or tear film can be related to properties of the matrixin which the therapeutic agent dissolves. In specific embodiments, therate of migration from the drug core to the tear or tear film can bebased on a silicone formulation. In some embodiments, the concentrationof therapeutic agent dissolved in the drug core may be controlled toprovide the desired rate of release of the therapeutic agent. Thetherapeutic agent included in the core can include liquid, solid, solidgel, solid crystalline, solid amorphous, solid particulate, and/ordissolved forms of the therapeutic agent. In a preferred embodiment, thedrug core comprises a silicone matrix containing the therapeutic agent.The therapeutic agent may comprise liquid or solid inclusions, forexample liquid Latanoprost droplets or solid Bimatoprost particles,respectively, dispersed in the silicone matrix.

The drug core can comprise one or more biocompatible materials capableof providing a sustained release of the therapeutic agent. Although thedrug core is described above with respect to an embodiment comprising amatrix with a substantially non-biodegradable silicone matrix withinclusions of the drug located therein that dissolve, the drug core caninclude structures that provide sustained release of the therapeuticagent, for example a biodegradable matrix, a porous drug core, liquiddrug cores and solid drug cores. A matrix that contains the therapeuticagent can be formed from either biodegradable or non-biodegradablepolymers. A non-biodegradable drug core can include silicone, acrylates,polyethylenes, polyurethane, polyurethane, hydrogel, polyester (e.g.,DACRON® from E. I. Du Pont de Nemours and Company, Wilmington, Del.),polypropylene, polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE),polyether ether ketone (PEEK), nylon, extruded collagen, polymer foam,silicone rubber, polyethylene terephthalate, ultra high molecular weightpolyethylene, polycarbonate urethane, polyurethane, polyimides,stainless steel, nickel-titanium alloy (e.g., NITANOL®), titanium,stainless steel, cobalt-chrome alloy (e.g., ELGILOY® from ElginSpecialty Metals, Elgin, Ill.; CONICHROME® from Carpenter Metals Corp.,Wyomissing, Pa.). A biodegradable drug core can comprise one or morebiodegradable polymers, such as protein, hydrogel, polyglycolic acid(PGA), polylactic acid (PLA), poly(L-lactic acid) (PLLA),poly(L-glycolic acid) (PLGA), polyglycolide, poly-L-lactide,poly-D-lactide, poly(amino acids), polydioxanone, polycaprolactone,polygluconate, polylactic acid-polyethylene oxide copolymers, modifiedcellulose, collagen, polyorthoesters, polyhydroxybutyrate,polyanhydride, polyphosphoester, poly(alpha-hydroxy acid) andcombinations thereof. In some embodiments the drug core can comprise atleast one of hydrogel polymer.

Release of Therapeutic Agent at Effective Levels

The rate of release of the therapeutic agent can be related to theconcentration of therapeutic agent dissolved in the drug core. In manyembodiments, the drug core comprises non-therapeutic agents that areselected to provide a desired solubility of the therapeutic agent in thedrug core. The non-therapeutic agent of the drug core can comprisepolymers as described herein and additives. A polymer of the core can beselected to provide the desired solubility of the therapeutic agent inthe matrix. For example, the core can comprise hydrogel that may promotesolubility of hydrophilic treatment agent. In some embodiments,functional groups can be added to the polymer to provide the desiredsolubility of the therapeutic agent in the matrix. For example,functional groups can be attached to silicone polymer.

In some embodiments, additives may be used to control the releasekinetics of therapeutic agent. For example, the additives may be used tocontrol the concentration of therapeutic agent by increasing ordecreasing solubility of the therapeutic agent in the drug core so as tocontrol the release kinetics of the therapeutic agent. The solubilitymay be controlled by providing appropriate molecules and/or substancesthat increase and/or decrease the solubility of the dissolved from ofthe therapeutic agent to the matrix. The solubility of the dissolvedfrom the therapeutic agent may be related to the hydrophobic and/orhydrophilic properties of the matrix and therapeutic agent. For example,surfactants, tinuvin, salts and water can be added to the matrix and mayincrease the solubility of hydrophilic therapeutic agent in the matrix.In addition, oils and hydrophobic molecules and can be added to thematrix and may increase the solubility of hydrophobic treatment agent inthe matrix.

Instead of or in addition to controlling the rate of migration based onthe concentration of therapeutic agent dissolved in the matrix, thesurface area of the drug core can also be controlled to attain thedesired rate of drug migration from the core to the target site. Forexample, a larger exposed surface area of the core will increase therate of migration of the treatment agent from the drug core to thetarget site, and a smaller exposed surface area of the drug core willdecrease the rate of migration of the therapeutic agent from the drugcore to the target site. The exposed surface area of the drug core canbe increased in any number of ways, for example by any of castellationof the exposed surface, a porous surface having exposed channelsconnected with the tear or tear film, indentation of the exposedsurface, protrusion of the exposed surface. The exposed surface can bemade porous by the addition of salts that dissolve and leave a porouscavity once the salt dissolves. Hydrogels may also be used, and canswell in size to provide a larger exposed surface area. Such hydrogelscan also be made porous to further increase the rate of migration of thetherapeutic agent.

Further, an implant may be used that includes the ability to release twoor more drugs in combination, such as the structure disclosed in U.S.Pat. No. 4,281,654 (Shell). For example, in the case of glaucomatreatment, it may be desirable to treat a patient with multipleprostaglandins or a prostaglandin and a cholinergic agent or anadrenergic antagonist (beta blocker), such as ALPHAGAN®, or aprostaglandin and a carbonic anhydrase inhibitor.

In addition, drug impregnated meshes may be used such as those disclosedin US Patent Publication No. 2002/0055701 or layering of biostablepolymers as described in US Patent Publication No. 2005/0129731. Certainpolymer processes may be used to incorporate drug into the devices ofthe present invention such as, so-called “self-delivering drugs” orPolymerDrugs (Polymerix Corporation, Piscataway, N.J.) are designed todegrade only into therapeutically useful compounds and physiologicallyinert linker molecules, further detailed in US Patent Publication No.2005/0048121 (East), hereby incorporated by reference in its entirety.Such delivery polymers may be employed in the devices of the presentinvention to provide a release rate that is equal to the rate of polymererosion and degradation and is constant throughout the course oftherapy. Such delivery polymers may be used as device coatings or in theform of microspheres for a drug depot injectable (such as a reservoir ofthe present invention). A further polymer delivery technology may alsobe adapted to the devices of the present invention such as thatdescribed in US Patent Publication No. 2004/0170685 (Carpenter), andtechnologies available from Medivas (San Diego, Calif.).

In specific embodiments, the drug core matrix comprises a solidmaterial, for example silicone, that encapsulates inclusions of thedrug. The drug comprises molecules which are very insoluble in water andslightly soluble in the encapsulating drug core matrix. The inclusionsencapsulated by the drug core can be micro-particles having dimensionsfrom about 1 μm to about 100 μm across. The drug inclusions can comprisecrystals, for example Bimatoprost crystals, and/or droplets of oil, forexample with Latanoprost oil. The drug inclusions can dissolve into thesolid drug core matrix and substantially saturate the drug core matrixwith the drug, for example dissolution of Latanoprost oil into the soliddrug core matrix. The drug dissolved in the drug core matrix istransported, often by diffusion, from the exposed surface of the drugcore into the tear film. As the drug core is substantially saturatedwith the drug, in many embodiments the rate limiting step of drugdelivery is transport of the drug from the surface of the drug corematrix exposed to the tear film. As the drug core matrix issubstantially saturated with the drug, gradients in drug concentrationwithin the matrix are minimal and do not contribute significantly to therate of drug delivery. As surface area of the drug core exposed to thetear film is nearly constant, the rate of drug transport from the drugcore into the tear film can be substantially constant. Work in relationwith the present invention suggests that the solubility of thetherapeutic agent in water and molecular weight of the drug can effecttransport of the drug from the solid matrix to the tear. In manyembodiments, the therapeutic agent is nearly insoluble in water and hasa solubility in water of about 0.03% to 0.002% by weight and a molecularweight from about 400 grams/mol. to about 1200 grams/mol.

In many embodiments the therapeutic agent has a very low solubility inwater, for example from about 0.03% by weight to about 0.002% by weight,a molecular weight from about 400 grams per mole (g/mol.) to about 1200g/mol, and is readily soluble in an organic solvent. Cyclosporin A (CsA)is a solid with an aqueous solubility of 27.67 μg/mL at 25° C., or about0.0027% by weight, and a molecular weight (M.W.) of 1202.6 g/mol.Latanoprost (Xalatan) is a prostaglandin F2α analogue, a liquid oil atroom temperature, and has an aqueous solubility of 50 μg/mL in water at25° C., or about 0.005% by weight and a M.W. of 432.6 g/mol. Bimatoprost(Lumigan) is a synthetic prostamide analogue, a solid at roomtemperature solubility in water of 300 μg/mL in water at 25° C., or0.03% by weight, and has a M.W. of 415.6 g/mol.

Work in relation with the present invention indicates that naturallyoccurring surfactants in the tear film, for example surfactant D andphospholipids, may effect transport of the drug dissolved in the solidmatrix from the core to the tear film. The drug core can be adapted inresponse to the surfactant in the tear film to provide sustaineddelivery of the drug into the tear film at therapeutic levels. Forexample, empirical data can be generated from a patient population, forexample 10 patients whose tears are collected and analyzed forsurfactant content. Elution profiles in the collected tears for a drugthat is sparingly soluble in water, for example cyclosporine, can alsobe measured and compared with elution profiles in buffer and surfactantsuch that an in vitro model of tear surfactant is developed. An in vitrosolution with surfactant based on this empirical data can be used toadjust the drug core in response to the surfactant of the tear film.

The drug cores may also be modified to utilize carrier vehicles such asnanoparticles or microparticles depending on the size of the molecule tobe delivered such as latent-reactive nanofiber compositions forcomposites and nanotextured surfaces (Innovative Surface Technologies,LLC, St. Paul, Minn.), nanostructured porous silicon, known asBioSilicont, including micron sized particles, membranes, woven fibersor micromachined implant devices (pSividia, Limited, UK) and proteinnanocage systems that target selective cells to deliver a drug(Chimeracore).

In many embodiments, the drug insert comprises of a thin-walledpolyimide tube sheath with a drug core comprising Latanoprost dispersedin Nusil 6385 (MAF 970), a medical grade solid silicone that serves asthe matrix for drug delivery. The distal end of the drug insert issealed with a cured film of solid Loctite 4305 medical grade adhesive.The drug insert may be placed within the bore of the punctum plug, theLoctite 4305 adhesive does not come into contact with either tissue orthe tear film. The inner diameter of the drug insert can be 0.32 mm; andthe length can be 0.95 mm. Three Latanoprost concentrations in thefinished drug product can be tested clinically: Drug cores can comprise3.5, 7 or 14 μg Latanoprost, with percent by weight concentrations of 5,10 and 20% respectively. Assuming an overall elution rate ofapproximately 100 ng/day, the drug core comprising 14 μg of Latanoprostis adapted to deliver drug for approximately at least 100 days, forexample 120 days. The overall weight of the drug core, includingLatanoprost, can be ˜70 μg. The weight of the drug insert including thepolyimide sleeve can be approximately 100 μg.

In many embodiments, the drug core may elute with an initial elevatedlevel of therapeutic agent followed by substantially constant elution ofthe therapeutic agent. In many instances, an amount of therapeutic agentreleased daily from the core may be below the therapeutic levels andstill provide a benefit to the patient. An elevated level of elutedtherapeutic agent can result in a residual amount of therapeutic agentand/or residual effect of the therapeutic agent that is combined with asub-therapeutic amount of therapeutic agent to provide relief to thepatient. In embodiments where therapeutic level is about 80 ng per day,the device may deliver about 100 ng per day for an initial deliveryperiod. The extra 20 ng delivered per day can have a beneficial effectwhen therapeutic agent is released at levels below the therapeuticlevel, for example at 60 ng per day. As the amount of drug delivered canbe precisely controlled, an initial elevated dose may not result incomplications and/or adverse events to the patient.

Example 1 Latanoprost Drug Core Elution Data

Drug cores as described above have been fabricated with different crosssectional sizes of 0.006 inches, 0.012 inches, and 0.025 inches, anddrug concentrations of 5%, 10% and 20% in a silicone matrix. Theses drugcores can be made with a Syringe Tube and Cartridge Assembly, MixingLatanoprost with Silicone, and Injecting the mixture into a polyimidetube which is cut to desired lengths and sealed. The length of the drugcores were approximately 0.80 to 0.95 mm, which for a diameter of 0.012inches (0.32 mm) corresponds to total Latanoprost content in the drugcores of approximately 3.5 μg, 7 μg and 14 μg for concentrations of 5%,10% and 20%, respectively.

Syringe Tube and Cartridge Assembly. 1. Take polyimide tubing of threedifferent diameters 0.006 inches, 0.0125 inches and 0.025 inches. 2. Cutpolyimide tubing of different diameters to ˜15 cm length. 3. InsertPolyimide tubes into a Syringe Adapter. 4. Adhesive bond polyimide tubeinto luer adapter (Loctite, low viscosity UV cure). 5. Trim end ofassembly. 6. Clean the cartridge assembly using distilled water and thenwith methanol and dry it in oven at 60° C.

Mix Latanoprost with Silicone. Prepare Latanoprost. Latanoprost isprovided as a 1% solution in methylacetate. Place the appropriate amountof solution into a dish and using a nitrogen stream, evaporate thesolution until only the Latanoprost remains. Place the dish with theLatanoprost oil under vacuum for 30 minutes. Combine Latanoprost withsilicone. Prepare three different concentrations of Latanoprost (5%, 10%and 20%) in silicon Nusil 6385 and inject it into tubing of differentdiameters (0.006 in, 0.012 in and 0.025 inches) to generate 3×3matrixes. The percent of Latanoprost to silicone is determined by thetotal weight of the drug matrix. Calculation: Weight ofLatanoprost/(weight of Latanoprost+weight of silicone)×100=percent drug.

Inject tube. 1. Insert Cartridge and Polyimide tubes assembly into 1 mlsyringe. 2. Add one drop of catalyst, (MED-6385 Curing Agent) in thesyringe. 3. Force excess catalyst out of the polyimide tube with cleanair. 4. Fill syringe with silicone drug matrix. 5. Inject tube with drugmatrix until the tube is filled or the syringe plunger becomes toodifficult to push. 6. Close off the distal end of the polyimide tube andmaintain pressure until the silicone begins to solidify. 7. Allow tocure at room temperature for 12 hours. 8. Place under vacuum for 30minutes. 9. Place tube in right size trim fixture (prepared in house tohold different size tubing) and cut drug inserts to length (0.80-0.95mm).

Testing. Elution study (in vitro). 1. Place 10 plugs of same size andsame concentration per centrifuge tube and add 1.5 ml of 7.4 pH buffersolution to it. 2. Change the solvent with fresh 7.4 pH buffer afterappropriate time. 3. Take HPLC of the elutant at 210 nm with PDAdetector 2996 using Sunfire C18, 3 mm×10 mm column (Waters Corporation,Milford, Mass.). Acetonitrile and water mixture is used for gradientelution. Calibration was done in house before and after each analysis,using in-house standards with precisely weighed concentration ofLatanoprost. 4. Calculate the amount of drug release per day per devicefor different size tubings having different concentrations ofLatanoprost. 5. Plot elution rate vs area and concentration for day 1and day 14.

FIGS. 7A and 7B show elution data of Latanoprost at day 1 and day 14,respectively, for the three core diameters of 0.006, 0.012 and 0.025inches and three Latanoprost concentrations of approximately 5%, 11% and18%. Elution rate of the Latanoprost in nanograms (ng) per day isplotted versus percent concentration. These data show that the rate ofelution is mildly dependent on the concentration and strongly dependenton the exposed surface area at both time periods. At day 1, the 0.006inch, 0.012 inch and 0.025 inch diameter cores released about 200 ng,400 ng and 1200 ng of Latanoprost, respectively, showing that thequantity of Latanoprost released increases with an increased size of theexposed surface area of the drug core. For each tube diameter, thequantity of Latanoprost released is compared to the concentration ofdrug in the drug core with a least square regression line. For the0.006, 0.012 and 0.025 inch drug cores the slope of the regression linesare 11.8, 7.4 and 23.4, respectively. These values indicate that adoubling of concentration of the Latanoprost drug in the core does notlead to a doubling of the elution rate of the Latanoprost from the core,consistent with droplets of Latanoprost suspended in a drug core matrixand substantial saturation of the drug core matrix with Latanoprostdissolved therein, as described above.

At day 14, the 0.006 inch, 0.012 inch (0.32 mm) and 0.025 inch diametercores released about 25 ng, 100 ng and 300 ng of Latanoprost,respectively, showing that the quantity of Latanoprost releasedincreases with an increased size of the exposed surface area of the drugcore at extended periods of time, and that the quantity of Latanoprostreleased is mildly dependent on the concentration of therapeutic agentin the core. For each tube diameter, the quantity of Latanoprostreleased is compared to the concentration of drug in the drug core witha least square regression line. For the 0.006, 0.012 and 0.025 inch drugcores the slope of the regression lines are 3.0, 4.3 and 2.2,respectively. For the 0.012 and 0.025 inch cores, these values indicatethat a doubling of concentration of the Latanoprost drug in the coredoes not lead to a doubling of the elution rate of the Latanoprost fromthe core, consistent with droplets of Latanoprost suspended in a drugcore matrix and substantial saturation of the drug core matrix withLatanoprost dissolved therein, as described above. However, for the0.006 inch diameter core, there is an approximately first orderrelationship between the quantity of initially in the core and theamount of drug released at day 14, which can may be caused by depletionof Latanoprost drug droplets in the core.

FIGS. 7D and 7E show dependence of the rate of elution on exposedsurface area of the drug core for the three core diameters and the threeconcentrations as in FIGS. 7A and 7B Latanoprost at day 1 and day 14,respectively, according to embodiments of the present invention. Elutionrate of the Latanoprost in nanograms (ng) per day is plotted versus theexposed surface area of the drug core in mm² as determined by thediameter of the drug core.

These data show that the rate of elution is mildly dependent on theconcentration of drug in the core and strongly dependent on the exposedsurface area at both one day and at 14 days. The exposed surface areasof the 0.006 inch, 0.012 inch and 0.025 inch diameter cores areapproximately 0.02, 0.07, and 0.32 mm², respectively. At day 1, the0.02, 0.07, and 0.32 mm², cores released about 200 ng, 400 ng and 1200ng of Latanoprost, respectively, showing that the quantity ofLatanoprost released increases with an increased size of the exposedsurface area of the drug core. For each concentration of therapeuticagent in the drug core, the quantity of Latanoprost released is comparedto the exposed surface area of the drug core with a least squareregression line. For the 5.1%, 11.2%, and 17.9% drug cores the slope ofthe regression lines are 2837.8, 3286.1 and 3411.6, respectively, withR² coefficients of 0.9925, 0.9701 and 1, respectively. At day 14, the0.02, 0.07, and 0.32 mm², cores released about 25 ng, 100 ng and 300 ngof Latanoprost, respectively showing that the quantity of Latanoprostreleased increases with an increased size of the exposed surface area ofthe drug core. For the 5.1%, 11.2%, and 17.9% drug cores the slope ofthe regression lines are 812.19, 1060.1 and 764.35, respectively, withR² coefficients of 0.9904, 0.9924 and 0.9663, respectively. These valuesindicate the elution rate of the Latanoprost from the core increaseslinearly with the surface area of the drug core, consistent with a drugsheath that can control the exposed surface area, as described above.The weak dependence of Latanoprost elution on concentration in the drugcore is consistent with droplets of Latanoprost suspended in a drug corematrix and substantial saturation of the drug core matrix withLatanoprost dissolved therein, as described above.

FIG. 7C shows elution data for Latanoprost from 0.32 mm diameter, 0.95mm long drug cores with concentrations of 5, 10 and 20% and drug weightsof 3.5, 7 and 14 μg, respectively, according to embodiments of thepresent invention. The drug cores were manufactured as described above.The elution rate is plotted in ng per day from 0 to 40 days. The 14 μgcore shows rates of approximately 100 ng per day from about 10 to 40days. The 7 μg core shows comparable rates from 10 to 20 days. Thesedata are consistent with droplets of Latanoprost suspended in a drugcore matrix and substantial saturation of the drug core matrix withLatanoprost dissolved therein, as described above.

Table 1 shows the expected parameters for each drug concentration. Asshown in FIG. 1C, in vitro results in a buffered saline elution systemshow that the plug initially elutes approximately 500 ng of Latanoprostper day, dropping off rapidly within 7-14 days to approximately 100ng/day, depending on the initial concentration of drug.

TABLE 1 Drug Elution Properties Total Latanoprost content 14 μg 7 μg 3.5μg In vitro elution rate See FIG. 1C See FIG. 1C See FIG. 1C Duration~100 days ~45 days ~25 days

In many embodiments, the duration of the drug core can be determinedbased on the calculated time when .about.10% of the original amount ofdrug remains in drug insert, for example where the elution rate levelsout and remains substantially constant at approximately 10 ng/day.

Example 2 Cyclosporin Drug Core Elution Data

Drug cores as described in Example 1 were made with cyclosporin having aconcentration of 21.2%. FIG. 8A shows elution profiles of cyclosporinfrom drug cores into a buffer solution without surfactant and into abuffer solution with surfactant, according to embodiments of the presentinvention. The buffer solution was made as described above. The solutionwith surfactant includes 95% buffer and 5% surfactant, UP-1005 UltraPure Fluid from Dow Corning, Midland Mich. Work in relation withembodiments of the present invention indicates that in at least someinstances, surfactants may be used in in vitro to model in situ elutionfrom the eye as the eye can include natural surfactants, for exampleSurfactant Protein D, in the tear film. The elution profile ofcyclosporin into surfactant is approximately 50 to 100 ng per day from30 to 60 days. Empirical data from tears of a patient population, forexample 10 patients, can be measured and used to refine the in vitromodel with appropriate amounts of surfactant. The drug core matrix maybe modified in response to the human tear surfactant as determined withthe modified in vitro model. The drug core can be modified in many waysin response to the human tear film surfactant, for example with anincreased exposed surface area and/or additives to increase an amount ofcyclosporine drug dissolved in the core, as described above, to increaseelution from the core to therapeutic levels, if appropriate.

Example 3 Bimatoprost Bulk Elution Data

Bulk samples of 1% Bimatoprost having a known diameter of 0.076 cm (0.76mm) were prepared. The height of each sample was determined from theweight and known diameter of the sample.

TABLE 2 Bulk Sample Size Weight Diameter Calculated Exposed SurfaceSample (mg) (cm) Height (cm) Area (cm²) 14-2-10 1.9 0.076 0.42 0.10914-2-11 1.5 0.076 0.33 0.088 14-2-12 1.9 0.076 0.42 0.109

The calculated heights ranged from 0.33 cm to 0.42 cm. The exposedsurface area on each end of each bulk sample was approximately 0.045cm², providing volumes of 0.019 cm and 0.015 cm³ for the 0.42 and 0.33cm samples, respectively. The exposed an exposed surface area of samplescalculated from the height and diameter without a drug sheath wasapproximately 0.1 cm². Three formulations were evaluated: 1) silicone4011, 1% Bimatoprost, 0% surfactant; 2) silicone 4011, 1% Bimatoprost,approximately 11% surfactant; and 3) silicone 4011, 1% Bimatoprost,approximately 33% surfactant. The elution data measured for the bulksamples with formulation 1, 2 and 3 were normalized to ng per device perday (ng/device/day) assuming a surface area of the bulk device is 0.1cm² and the surface area of the clinical device is 0.00078 cm² (0.3 mmdiameter). FIG. 9A shows normalized elution profiles in ng per deviceper day over 100 days for bulk sample of silicone with 1% Bimatoprost,assuming an exposed surface diameter of 0.3 mm on the end of the device,according to embodiments of the present invention. The normalizedelution profile is about 10 ng per day. The data show approximately zeroorder release kinetics from about ten days to about 90 days for each ofthe formulations. These data are consistent with particles ofBimatoprost suspended in a drug core matrix and substantial saturationof the drug core matrix with Bimatoprost dissolved therein, as describedabove. Similar formulations can be used with drug core sheaths and ashaped exposed surface of the core exposed to the tear to increase theexposed surface area as described above and deliver the drug intherapeutic amounts over an extended period.

In some embodiments, the core can comprise a 0.76 mm diameter core withan exposed surface diameter of 0.76 mm, corresponding to an exposedsurface area of 0.0045 cm². The core can be covered with a sheath todefine the exposed surface of the core as described above The normalizedelution profile for such a device, based on the bulk sample data above,is approximately 6 times (0.0045 cm²/0.00078 cm²) the elution profilefor the device with a 0.3 mm diameter exposed surface area. Thus, a zeroorder elution profile with an elution rate of about 60 ng per day can beobtained over a period of about 90 days. If the exposed surface area isincreased to about 0.0078 cm², for example with many of the exposedsurface shapes as described above, the zero order elution rat is about100 ng per day over a period of about 90 days. The concentration canalso be increased from 1%. Similar elution profiles can be obtained withLatanoprost.

Example 4 Latanoprost Elution Data

Drug cores were manufactured as described above with Latanoprost andsilicone 4011, 6385 and/or NaCl. Four formulations were manufactured asfollows: A) silicone 4011, approximately 20% Latanoprost, andapproximately 20% NaCL; B) silicone 4011, approximately 20% Latanoprost,and approximately 10% NaCl; C) silicone 4011, approximately 10%Latanoprost, and approximately 10% NaCl; and D) silicone 6385,approximately 20% Latanoprost. FIG. 10A shows profiles of elution ofLatanoprost form the cores for four formulations of Latanoprost,according to embodiments of the present invention. The results showinitial rates of approximately 300 ng per device per day that decreasesto about 100 ng per device per day by 3 weeks (21 days). The resultsshown are for non-sterile drug cores. Similar results have been obtainedwith sterile drug cores of Latanoprost. These data are consistent withdroplets of Latanoprost suspended in a drug core matrix and substantialsaturation of the drug core matrix with Latanoprost dissolved therein,as described above.

While the exemplary embodiments have been described in some detail, byway of example and for clarity of understanding, those of skill in theart will recognize that a variety of modification, adaptations, andchanges may be employed. For example, multiple delivery mechanisms maybe employed, and each device embodiment may be adapted to includefeatures or materials of the other, and further multiple features ormultiple materials may be employed in a single device. Hence, the scopeof the present invention may be limited solely by the appending claims.

What is claimed is:
 1. A punctal plug configured for insertion into alacrimal canaliculus of a patient, the punctal plug comprising: asilicone plug body comprising a drug insert; the drug insert comprising:a drug core comprising a therapeutic agent contained in a matrix, and animpermeable sheath body partially covering the drug core, wherein whenthe punctal plug is inserted into the lacrimal canaliculus of thepatient an exposed surface of the drug core is in direct contact withtear fluid to permit diffusion of the therapeutic agent into the tearfluid of the eye.
 2. The implant of claim 1, wherein the sheath body iscomprised of at least one of polyimide or polyethylene terephthalate. 3.The implant of claim 1, wherein the sheath body includes adistinguishing color that shows placement of one or more of the implantin the lacrimal canaliculus or the insert in the implant.
 4. The implantof claim 1, wherein the therapeutic agent comprises one or more of ananti-glaucoma medication, a prostaglandin, a non-steroidalanti-inflammatory drug (NSAID), a lubricant, a surfactant, an inhibitorof angiogenesis, peptides, proteins, or enzymes.
 5. The implant of claim1, wherein the therapeutic agent is selected from the group consistingof latanoprost, bimatoprost, timolol maleate, NSAID, travoprost, andcyclosporin.
 6. The implant of claim 5, wherein about 3 micrograms toabout 135 micrograms of latanoprost is present in the drug core.
 7. Theimplant of claim 5, wherein about 50 micrograms to about 100 microgramsof latanoprost is present in the drug core.
 8. The implant of claim 1,wherein the drug core comprises inclusions of the therapeutic agent in apolymer.
 9. The implant of claim 8, wherein the inclusions comprisedroplets and the therapeutic agent is latanoprost.
 10. The implant ofclaim 1, wherein the drug insert is further configured to release thetherapeutic agent for at least 21 days.
 11. The implant of claim 1,wherein the sheath body comprises a polyimide sheath body, and whereinthe drug core comprises: silicone and latanoprost.
 12. The implant ofclaim 1, wherein the matrix comprises a non-biodegradable polymer. 13.The implant of claim 12, wherein the non-biodegradable polymer isselected from the group consisting of silicone, an acrylate, apolyethylene, polyurethane, and polyester.
 14. The implant of claim 1,wherein the concentration of therapeutic agent in the drug core is atleast 20% by weight of the drug core.
 15. The implant of claim 1,wherein the drug core comprises a non-homogenous mixture of silicone andthe therapeutic agent.
 16. The implant of claim 1, wherein the druginsert has a diameter of about 0.006 inches to about 0.025 inches.
 17. Amethod for the treatment of glaucoma in an eye, the method comprising:placing a punctal plug in a lacrimal canaliculus of the eye, wherein thepunctal plug comprises; a silicone plug body comprising a drug insert;the drug insert comprising: a drug core comprising a therapeutic agentcontained in a matrix; and an impermeable sheath body, wherein the drugcore is positioned within the sheath body, wherein the sheath body isconfigured to provide aproximal exposed proximal end of the drug insertin direct contact with tear fluid that releases therapeutic agent to theeye when the drug insert is disposed within the punctal plug and thepunctal plug is inserted into the lacrimal canaliculus of a patient.